Command line fixes of various kinds

- StrLens need a +1 for the null terminator to end the resulting wchar_ts.
- The pyargv population loop was skipping a parameter.
- Removed -skill, -warp, -loadgame, -playdemo, since those will be handled by
  the game-specific modules. -game can be used to specify a game to play and
  skip the prompt for it.
- Don't prefix PyDoom.zip with a ./ since we don't need it, and 99% of the time
  it won't be in the current directory anyway.